The Philippines was bracing for possible floods and landslides as a tropical storm continued to strengthen Monday as it moved closer to the country's eastern seaboard.

Tropical Storm Rammasun was expected to intensify into a typhoon before making landfall Tuesday morning in Albay province, the government's weather bureau said.

Rammasun was about 500 kilometres east of eastern Legazpi city as of Monday afternoon, packing sustained winds of 110 kilometres per hour and gusts of up to 140 kph, government weather forecaster Rene Paciente said.

It entered Philippine territory on Sunday but was still over the sea.

Alexander Pama, executive director of the National Disaster Risk Reduction and Management Council, said the council's field offices in at least seven regions, including Metropolitan Manila, had been put on alert for landslides and flash floods.

''Our initial assessment is that there is not much on the wind. What we are wary about are landslides, flooding,'' Pama said.

Schools suspended classes Monday afternoon in some areas, including Manila, the capital.

Local officials urged sea vessels not to sail in the storm's path, readied relief goods and prepared for the possible evacuation of residents, especially in flood- and landslide-prone areas.

Rammasun's impact is expected to be felt in metropolitan Manila starting Tuesday morning and will be over the capital by early Wednesday before moving into the South China Sea through either Bataan or Zambales province in the northwest, forecasters said.

It is expected to be out of Philippine territory by Thursday, moving toward southern China.

Central Philippine provinces have not yet fully recovered from the massive devastation caused by Typhoon Haiyan last November.

Haiyan's strong winds and tsunami-like storm surges flattened towns, leaving at least 6300 people dead and more than 1000 missing.